I have the 2600mah Lipo battery hooked up to the USB / DC / Solar Lithium Ion/Polymer charger and outputted to a mintyboost.

Everything seems to work fine except the battery itself. It took over 9 hours to charge the first time via USB and then I tried to charge my phone with it the next day. I got maybe 5 minutes out of it before it stopped charging. I've since tried to charge the battery again and it takes forever before the green LED comes on. Again tried to charge my phone and it doesnt go very far.

If I plug the USB / DC / Solar Lithium Ion/Polymer charger in via USB and plug my phone intot he minty boost, it will go until charged, but that seems to just be using pass through at that point.

Done charging (green light) 4.19VWaited 2 hours 4.17VPlugged in phone 0.00V no connection for some reason, unplugged from charging board, 4.18V found after fiddling around for a few seconds, plug it back inCharging phone 3.85VDrops 0.01V every 60 seconds until it gets to 3.65V then drops out altogether down to 0.00V and phone stops chargingTotal charge time ~ 10 minutes

I still think theres an issue with the battery, is there some other way I can test it?

Ok new battery installed, still think I have an issue. Definitely better but: Gave it a full 6 hour charge today, light went green. Hooked it up to my Galaxy S3 and it went from 23% to only 54%. I never touched the phone until it stopped charging. I figured I should get at least a full charge out of a 2600mah battery. For reference the GS3 has a 2100mah li ion

No the phone was on, but let's make this simple. The charging unit/battery is hooked to an unmodified Mintyboost. It outputs 500 mA. So shouldn't a 2600mah battery output 500ma for 5 hours? This charge lasted around 1.5 hours.

Not quite so simple. 2600mAh @3.7v is not the same as 2600mAh @5v. Assuming 100% boost efficiency, your get an effective 1924 mAh @5v. With a more realistic 80% boost efficiency, that gives you 1539mAh, so at best you will get 3 hours.

The boost converter in the minty is rated for 500mA continuous. The actual current draw is determined by the load. Higher currents are possible up to a point. If the phone is pulling more than 500mA, the efficiency will suffer even more.

"A good scientist is a person with original ideas. A good engineer is a person who makes a design that works with as few original ideas as possible. There are no prima donnas in engineering" - Freeman Dyson